JP2012092482A - Treatment agent for synthetic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment agent that hardly causes the formation of fluffs for a long time and that can improve productivity of a polyester fiber for a tire cord spun under a severe condition.SOLUTION: The treatment agent for the synthetic fiber comprises a smoothing agent component (A) and an emulsifier component (B). The treatment agent for the synthetic fiber has the maximum hydrous viscosity at 25°C less than 10,000 mPa.s. Preferably, the smoothing agent component (A) is selected from the group consisting of: a monovalent fatty acid ester (A1) of a polyvalent alcohol; and straight or branched C1-C6 monovalent alcohol alkylene oxide adduct (A2).

Description

  The present invention relates to a treatment agent for synthetic fibers (hereinafter abbreviated as a treatment agent). More specifically, the present invention relates to a treating agent used in spinning and stretching processes for polyester fibers for tire cords.

  Various processing agents are used depending on the purpose in order to smoothly advance the spinning and drawing processes of polyester fibers for tire cords. In recent years, in order to improve productivity and quality, spinning and stretching speeds have been increased and heating elements such as stretching rollers have been increasingly heated. Since yarn is produced under such severe conditions, fluff and the like are likely to occur in the spinning and drawing processes. In particular, with the increase in the temperature of a heating body such as a drawing roller, there is a problem that the heat deterioration of the treatment agent is promoted and fluff is easily generated in a short time, and therefore the cleaning cycle is shortened and productivity is lowered. For this reason, it is desired that the treatment agent does not easily generate fuzz for a long time and can improve productivity. Conventionally, as a treatment agent with improved productivity, a treatment agent containing a polyvalent ester compound, an anionic surfactant and two kinds of hindered phenolic antioxidants (for example, Patent Document 1), dialkyl thiodipropionate Such as sulfur-containing diester compounds, phosphate compounds and hindered phenol-based antioxidants (for example, Patent Document 2), polyvalent ester compounds, ester compounds having a thioether group, secondary sulfonate compounds, organic phosphate compounds and Treatment agent containing hindered phenolic antioxidant (for example, Patent Document 3), sulfur-containing diester compound such as dialkyl thiodipropionate, treatment agent containing two types of hindered phenolic antioxidant and phosphate metal salt (For example, Patent Document 4), a polyvalent ester compound and Emissions hindered phenol process contains an antioxidant agent (for example, Patent Document 5), aromatic ester compounds, such as treating agent containing the organic carboxylic acids and various antioxidants (for example, Patent Document 6) have been proposed.

JP 59-21680 A JP-A-7-216735 JP-A-8-120563 Japanese Patent Laid-Open No. 10-325074 Japanese Patent Laid-Open No. 5-140870 Japanese Patent Application Laid-Open No. 2004-292961

  An object of the present invention is to provide a treatment agent that is less prone to fluff for a long time with respect to a polyester fiber for tire cords that is produced under severe conditions, and that can improve productivity.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have reached the present invention. That is, the present invention contains a smoothing agent component (A) and an emulsifier component (B), and has a maximum water viscosity at 25 ° C. of less than 10,000 mPa · s; % Of the emulsion, and the emulsion is attached to the synthetic fiber so as to be 0.1 to 3.0% by weight as a treating agent; and the synthetic fiber is treated by the treatment method. Synthetic fiber.

  The treatment agent of the present invention is excellent in uniform adhesion, smoothness and antistatic properties required in the spinning and drawing processes, and is also processed in the spinning, high drawing speed, and high temperature of the heating body such as a drawing roller. Since the accumulation amount of the agent heat-deteriorated product can be reduced, fluff is unlikely to occur, production can be continued for a long time, and the cleaning cycle can be extended.

The processing agent of this invention contains a smoothing agent component (A) and an emulsifier component (B).
(A) in the present invention includes a monohydric fatty acid ester (A1) of a polyhydric alcohol, a linear or branched monohydric alcohol alkylene oxide (hereinafter abbreviated as AO) adduct (A2) having 1 to 6 carbon atoms. Etc.

  Examples of (A1) include esters obtained from polyhydric alcohols having 3 to 6 carbon atoms and linear or branched monovalent fatty acids having 8 to 18 carbon atoms.

  As the polyhydric alcohol having 3 to 6 carbon atoms constituting (A1), a dihydric alcohol (1,4-butanediol, 1,6-hexanediol, neopentyl glycol, etc.) and a 3-6 polyhydric alcohol (glycerin, Trimethylolpropane, pentaerythritol, sorbitol, sorbitan, etc.).

  Examples of the linear or branched monovalent fatty acid having 8 to 18 carbon atoms constituting (A1) include caprylic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, lauric acid, tridecanoic acid, isotridecanoic acid, myristic acid, Examples include palmitic acid, stearic acid, isostearic acid, coconut oil fatty acid, palm oil fatty acid, hydrogenated castor oil fatty acid and hydrogenated beef tallow fatty acid.

  Examples of the linear or branched monohydric alcohol having 1 to 6 carbon atoms constituting (A2) include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and n-hexanol.

  Examples of AO constituting (A2) include C2-C12 AO, specifically ethylene oxide (hereinafter abbreviated as EO), propylene oxide (hereinafter abbreviated as PO), butylene. Examples thereof include oxide (hereinafter abbreviated as BO), tetrahydrofuran (hereinafter abbreviated as THF), styrene oxide (hereinafter abbreviated as SO), and the like. A known method can be applied to the addition of AO to a monohydric alcohol or polyhydric alcohol. For example, an AO adduct can be obtained by adding AO to monohydric alcohol or polyhydric alcohol in the presence of a catalyst. The reaction temperature is usually 10 to 180 ° C., and the reaction time is 1 to 48 hours. AO may be used alone or in combination of two or more. When two or more types of AO are added, the addition mode is not particularly limited, and may be random addition or block addition. Catalysts used for adding AO include alkali catalysts (such as potassium hydroxide and sodium hydroxide), acidic catalysts (perhalogen acid (salt), sulfuric acid (salt), phosphoric acid (salt) and nitric acid (salt). Etc.], metal alcoholate catalysts (such as sodium methylate and potassium butyrate) and the like.

  Specific examples of (A1) include, for example, hardened tallow fatty acid ester of neopentyl glycol, palm oil fatty acid ester of glycerin, lauric acid ester of trimethylolpropane, palm oil fatty acid ester of trimethylolpropane, and pelargonic acid ester of pentaerythritol. And 2-ethylhexanoic acid ester of pentaerythritol and coconut oil fatty acid ester of sorbitan.

Specific examples of (A2) include, for example, EO12 mol · PO9 mol random adduct of methanol, EO10 mol · PO7 mol random adduct of ethanol, EO12 mol · PO10 mol random adduct of isopropyl alcohol, and EO11 of n-butanol. Molar PO8 mol random adduct, n-butanol EO42 mol PO32 mol random adduct, n-hexanol EO9 mol PO7 mol random adduct, methanol PO12 mol EO9 mol block adduct, ethanol PO10 mol EO 7 mol block adduct, isopropyl alcohol PO 12 mol EO 10 mol block adduct, n-butanol PO 11 mol EO 8 mol block adduct, n-butanol PO 42 mol EO 32 mol adduct and n-hexanol Etc. PO9 mol · EO 7 mole block adduct.

(A) may use 2 or more types together suitably if desired.
Preferred among (A) is a linear or branched monohydric alcohol AO adduct (A2) having 1 to 6 carbon atoms, and more preferred are monohydric fatty acid esters (A1) of polyhydric alcohols and carbon. It is a combination of a linear or branched monohydric alcohol AO adduct (A2) having a number of 1 to 6, and particularly preferred are monohydric fatty acid ester (A1) of polyhydric alcohol and gel permeation chromatography (hereinafter referred to as In combination with a linear or branched monohydric alcohol AO random adduct (A2) having a weight average molecular weight (hereinafter abbreviated as Mw) measured by GPC of 800 to 5,000 and having 1 to 6 carbon atoms. is there.

The Mw of (A2) can be measured under the following conditions using GPC.
<Measurement conditions of Mw>
Model: HLC-8120 [manufactured by Tosoh Corporation]
Column: TSK gel SuperH4000
TSK gel SuperH3000
TSK gel SuperH2000
[Both made by Tosoh Corporation]
Column temperature: 40 ° C
Detector: RI
Solvent: Tetrahydrofuran Flow rate: 0.6 ml / min Sample concentration: 0.25% by weight
Injection volume: 10 μl
Standard: Polyoxyethylene glycol [manufactured by Tosoh Corporation; TSK STANDARD
POLYETHYLENE OXIDE]
Data processor: SC-8020 [manufactured by Tosoh Corporation]

  (B) in the present invention includes a linear or branched monohydric alcohol AO adduct (B1) having 8 to 18 carbon atoms, an AO adduct of a polyhydric alcohol fatty acid ester (B2), and an AO of an animal or vegetable oil having a hydroxyl group. Examples include adducts (B3) and fatty acid esters (B4) of (B3).

  (B1) is, for example, a linear or branched monohydric alcohol having 8 to 18 carbon atoms (octanol, 2-ethylhexanol, decanol, isodecanol, branched decanol, undecanol, isoundecanol, branched undecanol, dodecanol, isocho Dodecanol, branched dodecanol, tridecanol, isotridecanol, branched tridecanol, tetradecanol, pentadecanol, hexadecanol, octadecanol, isooctadecanol, branched octadecanol and oleyl alcohol)) Is mentioned. Specifically, EO11 mol / PO9 mol random adduct of n-octanol, EO12 mol / BO9 mol random adduct of 2-ethylhexanol, EO8 mol / THF 6 mol random adduct of isodecyl alcohol, 2-ethylhexanol EO 40 mol · PO 30 mol random adduct, isodecyl alcohol EO 38 mol · PO 28 mol random adduct, dodecanol EO 12 mol · PO 8 mol random adduct, tridecanol EO 13 mol · PO 7 mol random adduct, branched tridecanol EO 12 mol · PO9 mol random adduct, EO13 mol / PO9 mol random adduct of octadecanol, EO12 mol · PO7 mol random adduct of branched octadecanol, EO14 mol · PO10 mollan of oleyl alcohol N-octanol PO15 mol EO13 mol block adduct, 2-ethylhexanol PO15 mol EO12.5 mol block adduct, 2-ethylhexanol PO20 mol EO9 mol block adduct, decyl alcohol PO 15 mol · EO 12 mol block adduct, isodecyl alcohol PO 18 mol · EO 7 mol block adduct, dodecanol PO 12 mol · EO 8 mol block adduct, tridecanol PO 13 mol · EO 7 mol block adduct, branched tridecanol PO 12 mol · EO9 mol block adduct, PO13 mol of octadecanol, EO9 mol block adduct, PO12 mol of branched octadecanol, EO7 mol block adduct of oleyl alcohol, PO14 mol, EO10 mol of oleyl alcohol Such as lock adducts.

As (B2), an aliphatic polyvalent (3 to 6 valent) alcohol having 3 to 6 carbon atoms (glycerin, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, etc.) and an aliphatic carboxylic acid having 8 to 24 carbon atoms [ Aliphatic saturated carboxylic acids (caprylic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, lauric acid, tridecanoic acid, isotridecanoic acid, myristic acid, palmitic acid, stearic acid, and isostearic acid), aliphatic unsaturated carboxylic acids (Oleic acid, linoleic acid, linolenic acid, etc.), animal and vegetable oil fatty acids (such as coconut oil fatty acid, palm oil fatty acid, castor oil fatty acid, hardened castor oil fatty acid, beef tallow fatty acid, hardened tallow fatty acid and pork tallow fatty acid)] ester carbon number Examples thereof include 2 to 12 AO adducts.
Specifically, EO 15 mol adduct of glyceryl beef tallow fatty acid ester, EO 20 mol adduct of trimethylolpropane stearate ester, EO 30 mol adduct of oleic ester of pentaerythritol, EO 20 mol adduct of sorbitan oleate and sorbitol EO 40 mol adduct of stearic acid ester and the like can be mentioned.

  Examples of (B3) include AO adducts having 2 to 12 carbon atoms of animal and vegetable oils having hydroxyl groups (such as hydrogenated castor oil). Specific examples include EO 10 mol adduct of hydrogenated castor oil and EO 25 mol adduct of hydrogenated castor oil.

(B4) is an aliphatic carboxylic acid having 8 to 24 carbon atoms of [B3] [aliphatic saturated carboxylic acid (caprylic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, lauric acid, tridecanoic acid, isotridecanoic acid , Myristic acid, palmitic acid, stearic acid and isostearic acid), aliphatic unsaturated carboxylic acids (oleic acid, linoleic acid, linolenic acid, etc.), animal and vegetable oil fatty acids (coconut oil fatty acid, palm oil fatty acid, castor oil fatty acid, hardened) Castor oil fatty acid, beef tallow fatty acid, hardened beef tallow fatty acid, pork tallow fatty acid and the like)] ester and the like. Specific examples include stearic acid ester of castor oil EO 43 mol adduct, oleic acid ester of hydrogenated castor oil EO 20 mol adduct, and beef tallow fatty acid ester of castor oil EO 25 mol adduct.

(B) may be used in combination of two or more kinds as desired.
Preferred among (B) are linear or branched monohydric alcohol AO adducts (B1) having 8 to 18 carbon atoms, AO adducts of animal and vegetable oils having a hydroxyl group (B3), fatty acid esters of (B3) ( B4), and more preferred are linear or branched monohydric alcohol AO block adducts (B1) having 8 to 18 carbon atoms, fatty acid of AO adducts (B3) and (B3) of animal and vegetable oils having a hydroxyl group. It is a combined use of ester (B4).

The maximum water viscosity at 25 ° C. of the treatment agent of the present invention is less than 10,000 mPa · s. Here, the maximum water viscosity is the viscosity of the aqueous dispersion of a treating agent at 25 ° C. of a 10 to 90% by weight aqueous dispersion of the treating agent of the present invention, which is a digital B type viscometer “DVL-B type” [Tokyo Keiki Co., Ltd.]. (Made by Co., Ltd.) was measured twice, and the maximum of the hydrolyzed viscosity of the treatment agent aqueous dispersion when the average value was taken as the hydrolyzed viscosity was defined as the maximum hydrolyzed viscosity.
The maximum water viscosity at 25 ° C. is preferably less than 5,000 mPa · s, more preferably less than 3000 mPa · s. When the maximum water viscosity is 10,000 mPa · s or more, after the emulsion is fed, when the water evaporates, the viscosity of the treatment agent becomes too high and the cohesiveness of the treatment agent is reduced, and the uniform adhesion to the fiber yarn is reduced. As a result, smoothness and antistatic properties are reduced. In addition, the dispersibility of the treatment agent heat-deteriorated product deposited on a heated body such as a drawing roller at a high temperature is deteriorated and the amount of deposition is increased, so that the fiber yarn is easily caught on the deposit in the spinning and drawing process. Fluff occurs in a short time, and the cleaning cycle is shortened, resulting in decreased productivity.

  The weight ratio (A) / (B) between (A) and (B) is preferably 2.0 to 4.0. If it is 2.0 or more, smoothness is good, and if it is less than 4.0, it is preferable in terms of antistatic properties.

The processing agent of the present invention can be blended with any other known component (C) within a range not impairing its performance.
Examples of (C) include antioxidants, softeners (AO adducts of animal and vegetable oils having hydroxyl groups, polyesters of divalent fatty acids and monovalent fatty acids, etc.), pH adjusters (sodium hydroxide and potassium hydroxide, etc.) Amines such as alkalis, alkylamines and AO adducts of alkylamines, organic acids such as oleic acid), antistatic agents (such as phosphates and fatty acid soaps), silicones (such as polydimethylsiloxane and alkyl-modified silicones), Examples include ultraviolet absorbers, viscosity modifiers, and appearance modifiers. The content of these (C) is preferably 10% by weight or less with respect to the entire treatment agent.

In the method for treating synthetic fibers of the present invention, the treatment agent of the present invention is made into an emulsion of 5 to 30% by weight, and the emulsion becomes 0.1 to 3.0% by weight as a synthetic fiber treatment agent for the synthetic fibers. It is made to adhere.
As a method for attaching the treatment agent to the synthetic fiber, a known method can be used, and it can be applied before the spinning step, the drawing step or the winding using a roller or a guide oiling device. The adhesion amount of the treatment agent of the present invention to the synthetic fiber is usually 0.1 to 3.0% by weight with respect to the weight of the synthetic fiber before the treatment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this. In addition, the numerical value in a table | surface represents a weight part (active ingredient).

<Example 1>
Antioxidant (C-1) 0.5 parts by weight, Trimethylolpropane palm oil fatty acid triester (A1-1) 25.0 parts by weight, n-butanol EO11 mol · PO8 mol random adduct (A2-1) 29.0 parts by weight, 10.5 parts by weight of n-butanol EO 42 mol · PO 32 mol random adduct (A2-2), 2-ethylhexanol PO15 mol · EO 12.5 mol block adduct (B1-1) 8.0 Parts by weight, EO 20 mol adduct of sorbitan oleic acid triester (B2-1), 6.0 parts by weight of EO 25 mol adduct of hydrogenated castor oil (B3-1) and hydrogenated castor oil EO 20 mol adduct Of oleic acid triester (B4-1) was stirred and mixed at 50 to 80 ° C. for 1 hour. After homogenization, the mixture was cooled to 30 ° C., 2.5 parts by weight of pH adjuster (C-3), 1.5 parts by weight of antistatic agent (C-4-1), and 1.0 of silicones (C-5). The processing agent of Example 1 was prepared by adding parts by weight.

<Examples 2-8 and Comparative Examples 1-6>
Each component was mix | blended like Example 1 by the mixing | blending prescription of Table 1, and the processing agent of Examples 2-8 and Comparative Examples 1-6 was prepared.

  Using the treatment agents of Examples 1 to 8 and Comparative Examples 1 to 6 described in Table 1, the deposition property evaluation, smoothness evaluation, and antistatic evaluation of the heat-deteriorated product were performed. These results are shown in Table 1. The maximum water viscosity at 25 ° C. of the treatment agent is also shown in Table 1.

  The maximum water viscosity at 25 ° C. of the treatment agents prepared in Examples and Comparative Examples, the evaluation method for depositing heat-deteriorated products, the smoothness evaluation method using polyester tire cord yarn, and the antistatic property evaluation method are as follows. .

<Measurement method of maximum water viscosity at 25 ° C.>
10 to 90% by weight (in increments of 5% by weight) of an aqueous dispersion of the treatment agent was prepared, and the viscosity of the aqueous dispersion of the treatment agent at 25 ° C. was measured using a digital B-type viscometer “DVL-B type” [Tokyo Keiki ) Made] is used twice, and the average value is taken as the water viscosity. Among the hydration viscosities of the treatment agent aqueous dispersions of each concentration, the maximum one is defined as the maximum hydration viscosity.

<Deposition property evaluation method of heat treatment degradation products>
0.5 g of the adjusted treatment agent was precisely weighed in a petri dish made of SUS and heated at 240 ° C. for 8 hours, and then the residue rate of the heat-deteriorated product was measured. The lower the value, the better the depositability of the processing agent degradation product, and the less the fluff is generated in the spinning and drawing processes, and the cleaning cycle can be extended, and the productivity is improved.
[Criteria]
◎: Residue rate of heat-degraded product is less than 11.0% ○: Residue rate of heat-degraded product is 11.0% or more and less than 15.0% △: Residue rate of heat-degraded product is 15.0% or more and 25.0% Less than% x: Residual rate of heat-deteriorated product is 25.0%

<Smoothness evaluation method>
A test yarn obtained by adhering the prepared treating agent to a commercially available polyester tire cord yarn (1100 dtx) so as to be 1.0% by weight as a treating agent (pure component) was rubbed under conditions of a temperature of 25 ° C. and a humidity of 40%. The body (surface satin chrome plating, diameter 5 cm) was brought into contact with an initial load of 100 g, a yarn speed of 100 m / min, and a contact angle of 180 °, and the load (g) after contact was measured. It shows that smoothness is so favorable that a value is low.
[Criteria]
◎: Load is less than 220 g ○: Load is 220 g or more and less than 235 g Δ: Load is 235 g or more and less than 250 g ×: Load is 250 g or more

<Antistatic evaluation method>
A test yarn obtained by adhering the prepared treating agent to a commercially available polyester tire cord yarn (1100 dtx) so as to be 1.0% by weight as a treating agent (pure component) was rubbed under conditions of a temperature of 25 ° C. and a humidity of 40%. The body (surface satin chrome plating, diameter 5 cm) was contacted at an initial load of 10 g, a yarn speed of 100 m / min, and a contact angle of 360 °, and the triboelectric charge at the time of contact was measured using a current collector potentiometer. Judged by. The closer the value is to 0, the better the antistatic property.
[Criteria]
◎: Triboelectric charge amount is −50 V or more ○: Triboelectric charge amount is −100 V or more and less than −50 V Δ: Triboelectric charge amount is −200 V or more and less than −100 V ×: Triboelectric charge amount is less than −200 V

In addition, each component in Table 1 is as follows.
A1-1: Trimethylolpropane palm oil fatty acid triester A1-2: Pelargonic acid tetraester of pentaerythritol A2-1: n-butanol EO 11 mol PO8 mol random adduct A2-2: n-butanol EO42 mol, PO32 mol random adduct, A′1-1: thiodipropionic acid diester of 2-decyltetradecanol, A′2-1: oleic acid ester of 2-decyltetradecanol, A′3-1 : Dodecanol EO 3 mol adduct thiodipropionic acid diester B1-1: 2-ethylhexanol PO 15 mol EO 12.5 mol block adduct B1-2: Oleyl alcohol EO 5 mol adduct B2-1: Sorbitan oleic acid Triester EO 20 mol adduct B3-1: Hardened castor oil EO2 5 mol adduct B3-2: EO 10 mol adduct of hydrogenated castor oil B4-1: oleic acid triester of hydrogenated castor oil EO 20 mol adduct B'4-1: stearin of 24 mol adduct of trimethylolpropane EO Acid diester B′5-1: Trimethylolpropane EO 24 mol adduct lauric acid triester Antioxidant (C-1): Triethylene glycol-bis [3- (3-t-butyl-5-
Methyl-4-hydroxyphenyl) propionate]
-Softener (C-2): EO 25 mol adduct of hydrogenated castor oil and polyester of maleic acid and stearic acid-pH adjuster (C-3): EO 15 mol adduct of tallow alkylamine-Antistatic agent (C- 4-1): Phosphate ester potassium salt of oleyl alcohol (monoester / diester = 40/60)
Antistatic agent (C-4-2): Potassium oleate Silicone (C-5): Polydimethylsiloxane [viscosity 20 mm ² / s (25 ° C.)]

As is apparent from Table 1, it can be seen that the treatment agents of the present invention (Examples 1 to 8) are excellent in all of the depositability, smoothness, and antistatic properties of the heat treatment degradation product.
On the other hand, Comparative Examples 1 to 6, which are treatment agents having a maximum water viscosity at 25 ° C. of 10,000 mPa · s or more, do not satisfy all the performance items.

  The treatment agent of the present invention is excellent in smoothness and antistatic properties required in the spinning and drawing processes, and has been deteriorated due to heat treatment even in recent years in spinning, increasing the drawing speed, and increasing the temperature of heating elements such as drawing rollers. By reducing the amount of accumulated matter, fluff is unlikely to occur and production can be continued for a long time, and it is possible to extend the cleaning cycle, particularly suitable for spinning and stretching processes of polyester fiber for tire cords of emulsion oil supply system Can be used.

Claims (10)

  A treating agent for synthetic fibers containing a smoothing agent component (A) and an emulsifier component (B) and having a maximum water viscosity at 25 ° C. of less than 10,000 mPa · s.   The smoothing agent component (A) is one or more selected from the group consisting of a monohydric fatty acid ester (A1) of a polyhydric alcohol and a linear or branched monohydric alcohol alkylene oxide adduct (A2) having 1 to 6 carbon atoms. The processing agent for synthetic fibers according to claim 1.   The smoothing agent component (A) is a monohydric fatty acid ester (A1) of a polyhydric alcohol and a linear or branched monohydric alcohol alkylene oxide adduct (A2) having 1 to 6 carbon atoms. Treatment agent for synthetic fibers.   The emulsifier component (B) is a linear or branched monohydric alcohol alkylene oxide adduct (B1) having 8 to 18 carbon atoms, an alkylene oxide adduct (B2) of a polyhydric alcohol fatty acid ester, an alkylene of an animal or vegetable oil having a hydroxyl group. The processing agent for synthetic fibers according to any one of claims 1 to 3, which is one or more selected from the group consisting of the fatty acid ester (B4) of the oxide adduct (B3) and (B3).   The processing agent for synthetic fibers according to claim 2 or 3, wherein (A1) is a linear or branched monovalent fatty acid ester having 8 to 18 carbon atoms of trimethylolpropane.   The (A2) is a random adduct of propylene oxide and ethylene oxide of a linear or branched monohydric alcohol having 1 to 6 carbon atoms, and has a weight average molecular weight of 800 to 5,000. Treatment agent for synthetic fibers.   The weight ratio (A) / (B) of (A) and (B) is 2.0-4.0, The processing agent for synthetic fibers of any one of Claims 1-6.   The treatment agent for synthetic fibers according to any one of claims 1 to 7 is made into an emulsion of 5 to 30% by weight, and the emulsion becomes 0.1 to 3.0% by weight as a synthetic fiber treatment agent for the synthetic fibers. A synthetic fiber treatment method characterized by adhering in such a manner.   The method for treating a synthetic fiber according to claim 8, wherein the synthetic fiber is a polyester fiber for tire cords.   Synthetic fiber processed by the processing method according to claim 8 or 9.